In a projection image displaying device such as a liquid crystal projector or the like, a short projection displaying device in which a projection mirror (a reflection mirror) for folding an optical path is provided between a projection lens and a projecting plane (such as a screen or the like) to reduce the distance between it and the projecting plane is marketed. In addition, in installation modes of the projection image displaying device, various installation modes are possible depending on the application such as not only floor installation that it is installed on a desk or the like, but also suspended installation that it is suspended from a ceiling, upward projection installation that projection is performed toward a ceiling or the like, downward projection installation that projection is performed toward a desk or the like and others.
In these projection image displaying devices, light generated from a light source such as a mercury lamp or the like is radiated to an image display device such as a liquid crystal panel or the like, and imaging light from the display device is enlarged and projected onto a screen via a projection lens. Since the light source such as the mercury lamp or the like is used in a sealed state, its temperature becomes high, and the display device is heated by being irradiated with light from the light source and its temperature rises. Since excessive temperature rise reduces the life of the light source and causes deformation of the display device and image deterioration, cooling air is sent from a cooling fan to the light source and the display device to suppress temperature rise. The cooling air used for this, external air on the outside of device is made to be introduced through an air inlet by a suction fan, to be blown against the light source and the display device and thereafter to be discharged to the outside of device through an exhaust port.
In order to effectively cool the light source and the display device, the wind velocity of the cooling air and the structure of a flow path become important. For example, in a projector device described in Patent Document 1, there is disclosed a configuration for maintaining a light source lamp at an appropriate temperature in various installation states of the device, that is, in the floor installation and the suspended installation, and in addition even when it is used in the upward projection installation and the downward projection installation. In this configuration, an attitude sensor for sensing an installed attitude of the projector device, and a control unit for controlling a fan in accordance with the attitude that the attitude sensor has sensed are provided.